Fig. 4.

Intra-accumbal injections of the dopamine D2/3 receptor antagonist raclopride blocked the acquisition but not the retention of conditioned relief. a Histological verification of the AcbSh injection sites of vehicle and raclopride into the AcbSh. In separate groups of rats, injections were performed either before conditioning (filled circles), or before testing on conditioned relief (filled squares). b Reactivity to foot shocks (FS) after vehicle and raclopride injections (n = 9/group), measured by the mean locomotor response during shock application (duration: 1 s). Increasing footshock intensities resulted in higher reactivity; however, raclopride injections had no effects. c Intra-AcbSh raclopride injections before relief conditioning significantly blocked relief learning (vehicle: n = 9; 0.5 µg raclopride: n = 8; 1.0 µg raclopride: n = 9), whereas d raclopride injections before the retention test (n = 16) had no effects. ^#p < 0.05 post hoc Dunnett’s comparison with vehicle difference score; **p < 0.01, *p < 0.05, post hoc Sydak’s multiple comparisons startle alone vs. CS-startle